Border Patrol agents decided on their own to fire beanbags at a group of armed illegal immigrants in a confrontation late last year near Nogales in which an agent was killed, the agency's commissioner said Friday.

Alan Bersin, Customs and Border Protection commissioner, said the agents' initial use of the beanbags was not mandated by agency policy, which allows agents to determine whether to use deadly or non-deadly force based on the threat.

Agent Brian Terry died after being shot in the back in a shootout between agents and suspected border bandits Dec. 14 near Peck Canyon, outside Nogales.

Terry and the other agents involved in the gunfight had M4 rifles and were authorized to use them, Bersin said.

"The decisions that were made about the use first of non-lethal force was a decision that was made by the team itself based on their knowledge of the circumstances," Bersin said in a news conference in Tucson on Friday. "This is not something that was micromanaged from Bortac headquarters in Washington or not something that the sector overrode.

"There is no policy and, was no standing policy, regarding the use of non-lethal force as a prelude to the use of lethal force," Bersin said. "This is very important for the people of Arizona and the people of America to understand. The agents were armed as they needed to be. They were prepared to use lethal force and did."

After the suspected bandits shot at the agents, two agents fired back, one with his long gun and one with his pistol, and FBI document filed in federal court shows. Terry died at the scene.

Why they made that decision and the exact sequence of events of the gunfight will come out at the conclusion of the investigation being carried out by the FBI, Bersin said.

Terry, 40, of Michigan, was a member of a specially trained tactical unit known as Bortac. On the night of the shooting, Terry and his crew were targeting a "rip crew" that robbed and assaulted drug runners and illegal immigrants, said Homeland Security Secretary Janet Napolitano.

While Bersin was clarifying the lethal-force policy in Tucson, Napolitano sent a letter Friday to Sen. Charles Grassley, R-Iowa, explaining the policy. Grassley questioned Napolitano about the policy during a Senate Judiciary Committee hearing Wednesday.

She wrote that the agency's policy authorizes agents to "use deadly force when they have a reasonable belief that a subject poses an immediate danger of death or serious physical injury" to the agent or another another person.

"CBP law enforcement personnel have never been ordered - now or in the past - to use less-lethal devices before using deadly force," Napolitano wrote. "Our officers and agents are empowered to determine the appropriate level of force in defense of themselves, their fellow officers and agents, or innocent third parties."

The Border Patrol's policy regarding use of force mirrors that of all law enforcement agencies, including the Justice Department, an agency spokesman said.

Grassley has also questioned the Justice Department about allegations that the Bureau of Alcohol, Tobacco, Firearms and Explosives allowed a gun smuggler it was investigating to purchase and smuggle the weapons eventually used in the shootout in which Terry died into Mexico. The Justice Department has denied the allegations, but Grassley continues to insist the claims are valid.

Bersin declined to comment about the gun-smuggling allegations during Friday's news conference, citing the ongoing FBI investigation.

No arrests have been made in the killing. The U.S. Attorney's Office in Arizona said investigators and prosecutors aim to bring criminal charges against the people responsible for Terry's slaying.

One man is in custody who was arrested near the shooting site that night. The man, Manuel Osorio-Arellanes, has not been charged in connection with the shooting. Osorio-Arellanes has been charged only with illegal re-entry after deportation and faces a May 10 trial.

The other three illegal immigrants from Mexico arrested immediately after the shooting have been cleared in the crime and were deported.

Terry, 40, was the 10th agent to die on duty in the Border Patrol's Tucson Sector since 1926 and the first agent shot to death in the Sector since 1998. Terry was buried in his hometown near Detroit on Dec. 22, and hundreds attended his memorial service January in Tucson.

Contact reporter Brady McCombs at 573-4213 or